Activity determination of 133Xe by gamma-ray spectrometry

As both ¹³³Xe and ¹³³Ba decay to the same daughter nucleus ¹³³Cs, the activity of a ¹³³Xe source can be determined spectrometrically by comparing the gamma-ray count-rate of the 81 keV full energy peak from ¹³³Xe with the same peak of a ¹³³Ba standard source. By choosing the same gamma transition in both cases, the measuring uncertainty is considerably reduced.     

Nuclear fusion between heavy ions by the gamma-ray spectroscopy method

The in-beam and off-beam gamma-ray spectroscopy method, as a tool for the study of nuclear fusion between heavy ions, is described. These methods allow the study of the production and decay of the compound nucleus, inelastic scattering and transfer reactions. In this work we report the determination of fusion cross sections at energies near and below the Coulomb barrier for a series of systems: targets of ^46,50Ti, ⁵⁹Co and ^64,66Zn bombarded by ¹⁴N and ¹⁶O projectiles. Cross sections from 0.4 to 1000 mb were measured.     

Size determination of silver clusters by time-of-flight mass spectroscopy and electron microscopy

The determination of size distribution is sought via time-of-flight mass spectroscopy and electron microscopy of neutral silver clusters produced by the inert gas condensation method. By adjusting suitable parameters the mean size could be varied between a few tens and several hundreds of atoms per cluster. In particular, the influence exerted on the cluster size by ionization (fragmentation) and by deposition onto an amorphous carbon support film (migration) was assessed. The stabilization of clusters sampled on amorphous carbon films is discussed in detail.     

Ionization energy determination by the kinetic method

Ionization energies of organic compounds can be determined by the kinetic method by dissociation of radical cations of van der Waals complexes. The ionized dimeric complexes of benzene and substituted benzenes, generated in the ion source of a multiquadrupole instrument by gentle charge exchange chemical ionization using carbon disulfide as reagent gas, when mass-selected and allowed to undergo collision-induced dissociation with argon, yield only the two individual radical cations as products. The logarithm of the ratio of their ion abundances correlates linearly with their ionization energies. Using this linear relationship, the ionization energy of 3-iodobenzonitrile was determined to be 9.39 ± 0.05 eV, and this case serves to illustrate the application of the kinetic method in the determination of an unknown ionization energy. From the slope of the kinetic method plot, it is evident that the clusters are weakly bound (effective temperature, 1670 K). Strengths of this method are the simplicity of the procedure and its potential application to a wide variety of compounds.     

An ultrasonic time-of-flight equivalent flaw sizing method

One of the challenging tasks in the field of ultrasonic NDE is to obtain quantitative flaw size, shape, and orientation information. In an equivalent flaw sizing approach, flaws in a material are reconstructed in terms of a best-fit simple shape such as an ellipsoid or ellipse. In this work, a new time-of-flight equivalent (TOFE) flaw sizing method is developed for obtaining best-fit equivalent flaws from a relatively small number of timing measurements at different transducer orientations. The performance of the method is demonstrated on synthetic numerical data and with experiments, including examples of sizing in anisotropic composite materials and in welds.     

Direct determination of the peptide content in microspheres by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

A quantitative determination of peptides incorporated into poly(d,l-lactide-co-glycolide) microspheres by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was accomplished in a single step without pretreatment for extracting the peptide from the microsphere. The conventional extraction methods often underestimate the actual amount of peptide because of incomplete extraction from the microspheres or loss during the procedures. In this study, the microspheres dissolved in acetonitrile containing 0.1% trifluoroacetic acid were mixed with matrix solution containing the internal standard, and the peptide content was directly determined by MALDI-TOF MS. The drug content values determined by MALDI-TOF MS in both the leuprolide- and salmon calcitonin-incorporated microspheres were closer to the theoretical contents than those determined by the conventional extraction method. This method using MALDI-TOF MS could be a good alternative to time-consuming and less-accurate conventional methods.     

Spectral measurement of angular neutron flux on the restricted surface of slab assemblies by the time-of-flight method

An experimental method of neutron angular spectrum measurement in a slab geometry with D-T neutrons has been developed and its characteristics were examined. This method separates collided flux from uncollided flux. A neutron collimator restricts the measuring area on the surface of a slab assembly and the detector-collimator response function was determined. The time-of-flight method with two discrimination levels was adopted using an NE213 scintillation detector with pulse shape discrimination to obtain an accurate efficiency. Such measurements provide useful information in fusion blanket research. The results of the spectrum measurement were compared with calculated neutron spectra. The estimated overall error of the spectrum was within 5%.     

Sizing nanoparticles by time-of-flight spectrometry

Time-of-flight (TOF) spectrometry utilizing scattered light detection of particles passing discrete detection locations in an accelerating gas jet is used for rapid measurement of highly-resolved size distributions of dry powder, gas- or liquid-borne particles having diameter > 300 nm. Extension of the measurement range of this technique to include nanoparticles (< 100 nm diameter) is investigated using a theoretical model to predict the reduction in minimum, scattered-light-detectable, particle size, a limit which restricts present TOF instruments to particles above 300 nm diameter. A single set of preliminary measured data are compared with the theoretical-model predictions. Together, these results indicate that a TOF spectrometer can provide rapid, highly-resolved particle size distribution measurement of nanoparticle powders and suspensions down to ≈ 50 nm diameter.     

Improved neutron detection by gamma-ray spectroscopy

Most high-efficiency interactions for neutron detection are with thermal neutrons, and the detection of the prompt gamma radiation emitted as a result of thermal neutron absorption in specific materials was sometimes used. These materials are named converters, the most widespread being 10B, 113Cd or 73Ge (the last two materials are detector materials themselves for CdZnTe and HPGe detectors). However, for these materials, the main gamma-ray energies are relatively low (in the region 473-600 keV), and there are interferences from other gamma rays present in background. Different combinations of moderator-converter-detector systems were employed to optimise the system efficiency and signal-to-background ratio, using B, Cd, Gd and Cl converters and HPGe, NaI(Tl) and BGO detectors. When using a Cl converter, the 1164.7 keV peak seems to be a good choice when a HPGe spectrometer is used. A very practical material containing chlorine is PVC.     

On the determination of boundary stresses by the finite element method

The conventional finite element method has been modified to allow the elastic stresses along the free boundaries of a structure to be determined with improved accuracy. The results obtained by this 'modified' method are compared with both a photo-elastic and some traditional finite element solutions.     

Radiation-induced reduction of diuron by gamma-ray irradiation

Diuron degradation efficiencies and the proposed mechanism by gamma-ray irradiation were investigated. Several factors that might affect the degradation values were further examined. The UV absorbances at 200-400 nm and diuron concentration decreased with the increase of radiation dose. When diuron initial concentration was 18.5 mg L(-1) and 1.0 kGy was selected as the radiation dose, diuron removal value and loss of total organic carbon were 100 and 34.1%, respectively. However, the concentration of Cl- ion increased with the increase of radiation dose. The process could be depicted by first order reaction kinetics and the reaction was mainly caused by the reaction of diuron with .OH and eaq-. The degradation efficiency decreased with the increase of initial concentration at the same radiation dose. H2O2, HCO3-, NO3-, NO2-, CH3OH and humic acid as additives reduced the degradation efficiency. Furthermore, the increase of NO3-, NO2-, CH3OH and humic acid would result in the decrease of the degradation values. The pH value could affect the removal efficiency and the degradation process was enhanced in acid condition. The pH value became lower with increasing radiation dose after gamma-ray irradiation.     

Hydrogen determination in silicon nitride films by the nuclear recoil method

The highly sensitive nuclear recoil method was used to determine the hydrogen concentration in silicon nitride films deposited by the ammonolysis of monosilane. Combination of the data obtained using this method with internal reflection spectroscopy data allowed us to estimate the absorption cross section ε(λ = 3.3 μm) for the NH bonds present in the films. The value of (5.9±1.2) × 10^-20 cm² obtained for ε(λ = 3.3 μm) is more reliable than values reported previously.     

The determination of diffusion coefficients by the method of integral analogs

A new method is discussed for determining diffusion coefficients — the method of integral analogs. This method makes it possible to calculate diffusion coefficients from experimental results to higher accuracy than existing methods.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol.18, No.1, pp. 90–95, January, 1970.     

Thermal conductivity determination for nonmetallic media by the cylindrical probe method

The problem of thermal conductivity for an infinitely long composite cylinder is solved. The solution obtained permits analysis of a probe of finite dimensions and the contact resistance between probe and casing. The experimental methodology is described and results are presented for determination of thermal conductivity of aqueous solutions of nitric and sulfuric acid at low temperatures.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 20, No. 4, pp. 647–653, April, 1971.     

The determination of thermal conductivity by the method of coaxial cylinders

An expression is obtained for the thermal-conductivity coefficients of an investigated substance by the method of coaxial cylinders.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 19, No. 1, pp. 74–78, July, 1970.     

An iterative method for calculating gamma-ray build-up factors in multi-layer shields

Point kernel codes that simulate gamma-ray transport often use build-up factors to take scattered photons into account. This study introduces a new method, for computing multi-layer shield build-up factors. This method, based on an empirical formula for calculating double-layer shield build-up factors, is iterative. For an N-layer shield, each iteration of the method treats the first and the second layer of the shield. It replaces these layers by a single equivalent layer composed of an appropriate material and, hence, it turns the N-layer shield into an (N - 1)-layer shield. In order to determine the equivalent layer of an appropriate material, a neural network approach is developed: some neural networks trained on a large set of various configurations provide the equivalent material for any double-layer configuration. The method is implemented into MERCURE-6.3 straight-line attenuation code and is validated by comparison between MERCURE-6.3 results and reference data for one-dimensional geometries. Reference data obtained from transport calculations performed using the Sn transport code TWODANT. The comparisons prove the accuracy and sturdiness of the method.     

Estimation of response functions of moderating type neutron detectors by the time-of-flight method combined with a large lead pile

The energy dependent response functions of moderating type neutron detectors having cylindrical polyethylene moderators of 1, 3, 6 and 10 cm thicknesses were determined using the time-of-flight (TOF) technique. By combining the 35 MeV electron linear accelerator with a large lead pile of about 150 t, a pulsed neutron field which is rich in intermediate neutrons was formed and its spectrum at the standard measuring point for the TOF experiment was measured by a Li glass scintillator. In this kind of TOF, the neutron time delay in the polyethylene moderator due to multiple collisions with hydrogen was evaluated by the time dependent neutron transport Monte Carlo code, and compiled to the time response matrix. By using the neutron spectrum at the standard measuring point and the time response matrix, the energy dependent response functions of the moderating type neutron detectors were determined from the measured time spectra for the first time in a considerably wide energy range from a few eV to about 50 keV. The experimental response functions showed good agreement with the calculated results.